(1) Field of the Invention
The present invention generally relates to a vehicle running position detecting system, and more particularly to a vehicle running position detecting system for detecting a position, in a width direction of a road, of a vehicle moving on the road.
(2) Description of the Related Art
Conventionally, a system for detecting a position at which a vehicle travels on a road is disclosed, for example, in Japanese Laid-Open Application No.4-293109. In this system, white lines each of which indicates a boundary between lanes is recognized based on image information obtained by a video camera mounted on a vehicle. A position of the vehicle is then detected based on the recognition result.
Further, another system for detecting a running position of a vehicle has been proposed. In this system, magnetic fields generated by magnetic nails (magnets) positioned along a line on a road are detected by a magnetic sensor mounted in the vehicle. Based on detected states of the magnetic fields (e.g., detected levels of the magnetic fields), a distance (in the width direction of the road) from the line along which the vehicle should run is detected.
In the above system in which the running position of a vehicle is detected based on image information obtained from the video camera mounted in the vehicle, it is difficult to accurately recognize white lines based on the image information from the video camera at night and in bad weather conditions (e.g.,in fog or snow). Further, in the system in which the distance from the running line is detected using the magnetic fields generated by the magnetic nails positioned on the road, it is difficult to widely distribute, in the width direction of the road, each of the magnetic fields of the magnetic nails. The distance from the running line (the running position of the vehicle in the width direction of the road) which can be detected is small. Thus, the detected result can not be used as basic information for steering control in a wide range, for example, to change the running lane.